Blue-chip bank stock Visa Inc (NYSE:V) hit a March 21, all-time high of $290.96 on March 21, but has lost 7.5$260.38 while clinging to a fractional year-to-date lead, but a historically bullish signal that has never failed is now flashing on the charts.Per data from Schaeffer's Senior Quantitative Analyst Rocky White, V is trading within one standard deviation of its 320-day moving average. After the last two times Visa stock pulled bac ...